Train random forest classifier.
Dimensions:
M - number trees
F - number features
N - number input vectors
H - number classes
USAGE
forest = forestTrain( data, hs, [varargin] )
INPUTS
data - [NxF] N length F feature vectors
hs - [Nx1] or {Nx1} target output labels in [1,H]
varargin - additional params (struct or name/value pairs)
.M - [1] number of trees to train
.H - [max(hs)] number of classes
.N1 - [5*N/M] number of data points for training each tree
.F1 - [sqrt(F)] number features to sample for each node split
.split - ['gini'] options include 'gini', 'entropy' and 'twoing'
.minCount - [1] minimum number of data points to allow split
.minChild - [1] minimum number of data points allowed at child nodes
.maxDepth - [64] maximum depth of tree
.dWts - [] weights used for sampling and weighing each data point
.fWts - [] weights used for sampling features
.discretize - [] optional function mapping structured to class labels
format: [hsClass,hBest] = discretize(hsStructured,H);
OUTPUTS
forest - learned forest model struct array w the following fields
.fids - [Kx1] feature ids for each node
.thrs - [Kx1] threshold corresponding to each fid
.child - [Kx1] index of child for each node
.distr - [KxH] prob distribution at each node
.hs - [Kx1] or {Kx1} most likely label at each node
.count - [Kx1] number of data points at each node
.depth - [Kx1] depth of each node
EXAMPLE
N=10000; H=5; d=2; [xs0,hs0,xs1,hs1]=demoGenData(N,N,H,d,1,1);
xs0=single(xs0); xs1=single(xs1);
pTrain={'maxDepth',50,'F1',2,'M',150,'minChild',5};
tic, forest=forestTrain(xs0,hs0,pTrain{:}); toc
hsPr0 = forestApply(xs0,forest);
hsPr1 = forestApply(xs1,forest);
e0=mean(hsPr0~=hs0); e1=mean(hsPr1~=hs1);
fprintf('errors trn=%f tst=%f\n',e0,e1); figure(1);
subplot(2,2,1); visualizeData(xs0,2,hs0);
subplot(2,2,2); visualizeData(xs0,2,hsPr0);
subplot(2,2,3); visualizeData(xs1,2,hs1);
subplot(2,2,4); visualizeData(xs1,2,hsPr1);
See also forestApply, fernsClfTrain
Piotr's Computer Vision Matlab Toolbox Version 3.24
Copyright 2014 Piotr Dollar. [pdollar-at-gmail.com]
Licensed under the Simplified BSD License [see external/bsd.txt]